/* Based on Xiph libogg checksum calculation */
function crc32(str) {
	var crc_reg;
	var crc_lookup = crc32.table;

	for (var i=0; i<str.length; i++)
		crc_reg = (crc_reg<<8)^crc_lookup[((crc_reg >> 24)&0xff)^str.charCodeAt(i)]

	return crc_reg;
}

crc32.table = [
	0x00000000,0x04c11db7,0x09823b6e,0x0d4326d9,
	0x130476dc,0x17c56b6b,0x1a864db2,0x1e475005,
	0x2608edb8,0x22c9f00f,0x2f8ad6d6,0x2b4bcb61,
	0x350c9b64,0x31cd86d3,0x3c8ea00a,0x384fbdbd,
	0x4c11db70,0x48d0c6c7,0x4593e01e,0x4152fda9,
	0x5f15adac,0x5bd4b01b,0x569796c2,0x52568b75,
	0x6a1936c8,0x6ed82b7f,0x639b0da6,0x675a1011,
	0x791d4014,0x7ddc5da3,0x709f7b7a,0x745e66cd,
	0x9823b6e0,0x9ce2ab57,0x91a18d8e,0x95609039,
	0x8b27c03c,0x8fe6dd8b,0x82a5fb52,0x8664e6e5,
	0xbe2b5b58,0xbaea46ef,0xb7a96036,0xb3687d81,
	0xad2f2d84,0xa9ee3033,0xa4ad16ea,0xa06c0b5d,
	0xd4326d90,0xd0f37027,0xddb056fe,0xd9714b49,
	0xc7361b4c,0xc3f706fb,0xceb42022,0xca753d95,
	0xf23a8028,0xf6fb9d9f,0xfbb8bb46,0xff79a6f1,
	0xe13ef6f4,0xe5ffeb43,0xe8bccd9a,0xec7dd02d,
	0x34867077,0x30476dc0,0x3d044b19,0x39c556ae,
	0x278206ab,0x23431b1c,0x2e003dc5,0x2ac12072,
	0x128e9dcf,0x164f8078,0x1b0ca6a1,0x1fcdbb16,
	0x018aeb13,0x054bf6a4,0x0808d07d,0x0cc9cdca,
	0x7897ab07,0x7c56b6b0,0x71159069,0x75d48dde,
	0x6b93dddb,0x6f52c06c,0x6211e6b5,0x66d0fb02,
	0x5e9f46bf,0x5a5e5b08,0x571d7dd1,0x53dc6066,
	0x4d9b3063,0x495a2dd4,0x44190b0d,0x40d816ba,
	0xaca5c697,0xa864db20,0xa527fdf9,0xa1e6e04e,
	0xbfa1b04b,0xbb60adfc,0xb6238b25,0xb2e29692,
	0x8aad2b2f,0x8e6c3698,0x832f1041,0x87ee0df6,
	0x99a95df3,0x9d684044,0x902b669d,0x94ea7b2a,
	0xe0b41de7,0xe4750050,0xe9362689,0xedf73b3e,
	0xf3b06b3b,0xf771768c,0xfa325055,0xfef34de2,
	0xc6bcf05f,0xc27dede8,0xcf3ecb31,0xcbffd686,
	0xd5b88683,0xd1799b34,0xdc3abded,0xd8fba05a,
	0x690ce0ee,0x6dcdfd59,0x608edb80,0x644fc637,
	0x7a089632,0x7ec98b85,0x738aad5c,0x774bb0eb,
	0x4f040d56,0x4bc510e1,0x46863638,0x42472b8f,
	0x5c007b8a,0x58c1663d,0x558240e4,0x51435d53,
	0x251d3b9e,0x21dc2629,0x2c9f00f0,0x285e1d47,
	0x36194d42,0x32d850f5,0x3f9b762c,0x3b5a6b9b,
	0x0315d626,0x07d4cb91,0x0a97ed48,0x0e56f0ff,
	0x1011a0fa,0x14d0bd4d,0x19939b94,0x1d528623,
	0xf12f560e,0xf5ee4bb9,0xf8ad6d60,0xfc6c70d7,
	0xe22b20d2,0xe6ea3d65,0xeba91bbc,0xef68060b,
	0xd727bbb6,0xd3e6a601,0xdea580d8,0xda649d6f,
	0xc423cd6a,0xc0e2d0dd,0xcda1f604,0xc960ebb3,
	0xbd3e8d7e,0xb9ff90c9,0xb4bcb610,0xb07daba7,
	0xae3afba2,0xaafbe615,0xa7b8c0cc,0xa379dd7b,
	0x9b3660c6,0x9ff77d71,0x92b45ba8,0x9675461f,
	0x8832161a,0x8cf30bad,0x81b02d74,0x857130c3,
	0x5d8a9099,0x594b8d2e,0x5408abf7,0x50c9b640,
	0x4e8ee645,0x4a4ffbf2,0x470cdd2b,0x43cdc09c,
	0x7b827d21,0x7f436096,0x7200464f,0x76c15bf8,
	0x68860bfd,0x6c47164a,0x61043093,0x65c52d24,
	0x119b4be9,0x155a565e,0x18197087,0x1cd86d30,
	0x029f3d35,0x065e2082,0x0b1d065b,0x0fdc1bec,
	0x3793a651,0x3352bbe6,0x3e119d3f,0x3ad08088,
	0x2497d08d,0x2056cd3a,0x2d15ebe3,0x29d4f654,
	0xc5a92679,0xc1683bce,0xcc2b1d17,0xc8ea00a0,
	0xd6ad50a5,0xd26c4d12,0xdf2f6bcb,0xdbee767c,
	0xe3a1cbc1,0xe760d676,0xea23f0af,0xeee2ed18,
	0xf0a5bd1d,0xf464a0aa,0xf9278673,0xfde69bc4,
	0x89b8fd09,0x8d79e0be,0x803ac667,0x84fbdbd0,
	0x9abc8bd5,0x9e7d9662,0x933eb0bb,0x97ffad0c,
	0xafb010b1,0xab710d06,0xa6322bdf,0xa2f33668,
	0xbcb4666d,0xb8757bda,0xb5365d03,0xb1f740b4
];

function Ogg(stream, options) {
	var opts = options || {};
	this.stream = stream;
	this.pageExpr = new BitString(
	 "capturePattern:4/char,"
	+"version:1,"
	+"headerType:1,"
	+"granulePos:8,"
	+"serial:4,"
	+"sequence:4,"
	+"checksum:4,"
	+"pageSegments:1,"
	+"segments:pageSegments/char,"
	+"frames:_,", {
		bytes: true
	  , bigEndian: false
	});

	this.rawPages = [];
	this.pages = [];
	this.pageIdx = 0;

	this.frames = [];
	this.data = null;
	this.segments = [];

	this.unpacked = false;
	this.file = !!opts.file;
	this.error = (options||{}).error || function (e) {};
}

Ogg.CAPTURE_PATTERN = 0x4f676753; // "OggS"
Ogg.INVALID_CAPTURE_PATTERN = 1;

Ogg.prototype.magic = function (c) {
	var magic;

	magic |= (c[0] << 24);
	magic |= (c[1] << 16);
	magic |= (c[2] << 8);
	magic |= c[3];

	return magic;
}

Ogg.prototype.createPage = function (data) {
	return this.pageExpr.pack(data);
}

Ogg.prototype.parsePage = function (binStr) {
	var page = this.pageExpr.unpack(binStr),
		seg = page.segments;

	if (this.magic(page.capturePattern) != Ogg.CAPTURE_PATTERN) {
		this.error( { code: Ogg.INVALID_CAPTURE_PATTERN });
		return;
	}

	this.rawPages.push(binStr);

	page.bos = function () {
		return (this.header == 2);
	}

	page.cont = function () {
		return (this.header == 0);
	}

	page.eos = function () {
		return (this.header == 4);
	}

	// Pushes the ogg parsed paged
	this.pages.push(page);

	// Pushes the page frames
	this.frames.push(page.frames);
}

Ogg.prototype.pageOut = function () {
	return this.pages[this.pageIdx], (this.pageIdx += 1);
}

Ogg.prototype.pages = function () {
	return this.pages;
}

Ogg.prototype.demux = function () {
	if (this.unpacked) return;

	var begin, next = 0, str, frameIdx = 0;

	while(next >= 0) {

		// Fetches OGG Page begin/end
		var begin = this.stream.indexOf("OggS", next), tmp;
		next = this.stream.indexOf("OggS", begin + 4);

		// Fetch Ogg Raw Page
		str = this.stream.substring(begin, next != -1 ? next : undefined)

		// Parse and store the page
		this.parsePage(str);
	}

	// Fetch headers
	if (this.file) {
		frameIdx = 2;
		this.headers = this.frames.slice(0, frameIdx);
	}

	// Fetch Data
	this.data = this.frames.slice(frameIdx);
	for (var i = frameIdx; i<this.pages.length; ++i) {
		this.segments.push(this.pages[i].segments);
	}

	this.unpacked = true;
	return this.pages;
}

Ogg.prototype.mux = function (d, o) {
	function OggPageHeader(type, length, checksum) {
		return page = {
			capturePattern: [0x4f, 0x67, 0x67, 0x53]
		  , version: 0
		  , headerType: type
		  , granulePos: 0 // TODO
		  , serial: 406
		  , sequence: 0
		  , checksum: checksum || 0
		  , pageSegments: 1
		  , segments: [ length || 0 ]
		  , frames: ""
		};
	}

	function OggPageData(segments) {
		var p = OggPageHeader(0);
		p.pageSegments = segments.length;
		p.segments = segments;
		return p;
	}

	function chksum(str, c) {
		var buf = new ArrayBuffer(str.length);
		var bufView = new Uint8Array(buf);
		for (var i=0, len=str.length; i<len; i++) {
			bufView[i] = str.charCodeAt(i);
		}
		dv = new DataView(buf);
		dv.setUint32(22, c, true);

		return String.fromCharCode.apply(null, new Uint8Array(buf));
	}

	function hdrup(hdr, content) {
		var csum, str;
		csum = crc32(hdr + content);
		str = chksum(hdr, csum) + content;
		return str;
	}

	function frames(segments) {
		var sum = 0;
		for (var i=0; i<segments.length; ++i) {
			sum += segments[i];
		}
		return sum;
	}

	o=o||{};

	var str = "";
	var p = "";
	var hdr = d[0];
	// header page
	p = this.createPage(OggPageHeader(2,
			o.length || hdr.length, o.checksum))
	str = hdrup(p, hdr);
	if (d.length == 1)
		return str;

	var comments = d[1];
	// comments page
	p = this.createPage(OggPageHeader(0,
			o.length || comments.length, o.checksum));
	str += hdrup(p, comments);
	if (d.length == 2)
		return str;


	// data page
	var data = d[2];
	var segments = data[1].chunk(100)
	  , stream = String.fromCharCode.apply(null,
	  		new Uint8Array(data[0].buffer))
	  , a = 0
	  , b = 0
	  , len = segments.length;

	for (var i = 0; i < len; ++i) {
		var segchunk = segments[i];
		b += frames(segchunk);

		p = this.createPage(OggPageData(segchunk));
		str += hdrup(p, stream.substring(a, b));

		a = b;
	}
	return str;
}

Ogg.prototype.bitstream = function () {
	if (!this.unpacked)	return null;
	return this.data.join("");
};
